In contactless charging, conforming to a standard for contactless charging (non-contact charging) of an electronic equipment by mainly WPC (Wireless Power Consortium), an organization of manufacturers established for the purpose of specification development and promotion of Qi specification, such a system that enables contactless charging for a portable handset terminal of not less than 5 W, as an example, has been developed. The system is made up of a contactless charging pad (transmitter) conforming to the WPC specification and an apparatus to be charged (receiver) designed to cope with the contactless charging.
In a magnetic attraction type contactless charging pad that exploits a magnetic force for positioning (position aligning) an apparatus to be charged, position aligning between a power transmission coil provided in the contactless charging pad and a power reception coil provided in the apparatus to be charged is generally by exploiting an attractive force between the magnet disposed at the power transmission coil provided in the contactless charging pad and the other at a center or its vicinity of a power reception coil provided in the apparatus to be charged. In some of apparatuses to be charged, no magnet is provided, in which case the position aligning is done by referring to a mark for a placement position provided on the magnetic attraction charging pad.
In this sort of the magnetic attraction type charging pad, it may sometimes occur that the magnetic force from the contactless charging pad acts on the apparatus to be charged, such as portable handset terminal, thus presenting a problem as later discussed.
Patent Document 1 discloses a charging unit in which a voice coil of a loudspeaker is to be used also as a secondary coil for contactless charging.
Patent Document 2 discloses an arrangement in which a power supply unit includes a movable primary coil and an electronic equipment includes a stationary secondary coil, these two coils being used for positioning. That is, the primary coil is DC-driven and the secondary coil of the equipment is also DC-driven, in such a manner that an attractive force generated between the two coils and the movable coil is attracted towards the secondary coil. Power may then be then transmitted from the primary coil to the secondary coil by AC drive.
Patent Literature 1:    Japanese Patent Kokai Publication No. JP2010-35297A
Patent Literature 2:    Japanese Patent Kokai Publication No. JP2010-273453A